Frontier Airlines is offering a slew of cheap flights this week, including some at an eye-popping $29, to cities such as Orlando, Denver and Atlanta. But there is a catch or two to know.

The sale is tailored for for last-minute, end-of-summer getaways, with the flights available between Aug. 4 and Aug. 30. Those taking advantage need to move quickly, as these flights must be booked by this Wednesday, Aug. 2.

It covers a host of select routes, with Nashville to Orlando, Kansas City to Denver and Cleveland to Atlanta all going for $29 one way to members of Frontier's Discount Den program.

If you're not a member of Frontier's program, no worries: Those flights still go for $39.

Remember that Frontier is a bare-bones budget airline, though. The fares themselves are cheap, but the airline may ding you for extras such as carry-on bags and reserved seats.